1. Field of the Disclosure
The present disclosure relates generally to an apparatus and method for releasing a coiled tubing internal conduit(s) or line(s) from a bottom hole assembly. An anchor assembly may connect the internal conduit or line to a bottom hole assembly that is connected to the coiled tubing.
2. Description of the Related Art
Coiled tubing is used in various operations and maintenance tasks for oil and gas wells. Some of the coiled tubing applications involve the use of a conduit or line located inside of the coiled tubing, herein after referred to as an internal line. The internal line may be used to communicate between the surface and a bottom hole assembly or downhole tool. The communications provided by the internal line may be electrical, fiber optic, hydraulic, and/or mechanical in nature. The internal line may also be used to control and/or operate various functions of a downhole tool or bottom hole assembly.
Due to the length of coiled tubing strings and nature of the various applications for which coiled tubing strings are used, both the coiled tubing and the internal line may experience an overall change in length. This change in length may be due to temperature, mechanical, and/or hydraulic effects, or combinations of those effects. Often the internal line is anchored to a bottom hole assembly in an effort to minimize potential operational difficulties of working with a coiled tubing string and an internal line having different lengths.
One potential problem of performing various operations with coiled tubing is due to the small clearances between the coiled tubing and/or the bottom hole assembly and the casing/tubing. Because of the small clearances and also quite often wellbore conditions which involve debris or junk, it is possible for the bottom hole assembly or the coiled tubing to become stuck or wedged in the casing/tubing. Stuck coiled tubing or coiled tubing connected to a stuck bottom hole assembly may prevent the coiled tubing from being retrieved again from the wellbore, or the proper closure of a downhole safety valve (if installed) presenting possible safety issues. If efforts are unsuccessful to remove the stuck bottom hole assembly and/or coiled tubing from the wellbore, one option is to cut the coiled tubing at a predetermined depth and remove the upper portion or nearly all of it from the wellbore. A cutting tool may be run on a wireline down the coiled tubing to the predetermined depth to cut the coiled tubing. The removal of the cut upper portion of the coiled tubing allows the subsurface safety valve (if installed) to close while leaving the bottom hole assembly and a possible lower portion of the coiled tubing in the wellbore.
If an internal line is present in the coiled tubing, the internal line needs to be removed prior to running in the cutting tool on the wireline. Conventionally, the internal line has been removed by pulling on the internal line at the surface. The force required to disconnect the internal line must exceed the weight of the internal line plus the force used to anchor the internal line to the bottom hole assembly. This amount of force can reach in excess of 10,000 pounds. In deep and deviated wells, the force required to disconnect the internal line from the bottom hole assembly may approach or exceed the ultimate tensile strength of the internal line. The conventional method of disconnecting and removing the internal line limits the type and size of internal line that may be used within a coiled tubing string. The conventional disconnecting method requires a relatively strong internal line, which may result in using an internal line with a larger diameter and thus, smaller flow area within the coiled tubing string.
Depending on the application, the preferred internal line may not have the ultimate tensile strength required to disconnect from the bottom hole assembly by the conventional method. For example, the internal line may be a small diameter wire or capillary tube. While the internal line needs to have a strength sufficient enough to supports its own weight over its entire length, the internal line may not have sufficient strength to permit the application of a tension force at the surface to disconnect the internal line from the bottom hole assembly. For example, a preferred internal line for a specific application may only have an ultimate tensile strength of 1150 lbs or less, which is not sufficient to permit disconnection by pulling on the internal line at the surface. The application of a tension force at the surface in an effort to disconnect the internal line from the bottom hole assembly may instead cause the internal line to break potentially leaving length of the internal line within the coiled tubing that is still connected to the bottom hole assembly. The presence of the internal line in the coiled tubing may prevent the use of a wireline cutting tool to cut off the coiled tubing at the predetermined depth, which may be below the subsurface safety valve, if one is installed.
The present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the issues set forth above.